function go_up(){
	var gallery = $A($$('#gal_images li'));
	if(!gallery[0].visible()) {
		var prev_el = gallery[0];
		gallery.each(function(s, index){
			if((s.visible()) && (!prev_el.visible())) {
				prev_el.show();
			}
			else if((!s.visible()) && (prev_el.visible())) {
				prev_el.hide();
			}
			prev_el = s;
		});
		prev_el.hide();
	} else {
		/* wir sind schon ganz oben */
	}
}
function go_down(){
	var gallery = $A($$('#gal_images li'));
	if(!gallery[gallery.length-1].visible()) {
		var prev_el = gallery[gallery.length-1];
		var counter = 1;
		gallery.each(function(s, index){
			if((s.visible()) && (!prev_el.visible()) && (counter == 1)) {
				s.hide();
				counter++;
			}
			else if((!s.visible()) && (prev_el.visible()) && (counter == 2)) {
				s.show();
				counter++;
			}
			prev_el = s;
		});
	} else {
		/* wir sind schon ganz unten */
	}
}